Corrosion-inhibiting compositions containing dialkyl sulfides or sulfoxides

ABSTRACT

CORROSION OF METAL SURFACES IN AN ACIDIC ENVIRONMENT IS REDUCED BY THE USE OF CORROSION INHIBITOR COMPOSITIONS COMPRISING A MIXTURE OF AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF DIALKYL SULFIDES AND DIALKYL SULFOXIDES AND AT LEAST ONE SURFACE-ACTIVE AGENT.

United States Patent Ofiice 3,809,655 Patented May 7., 1974 3,809,655 CORROSION-INHIBITING COMPOSITIONS CON- TAINING DIALKYL SULFIDES OR SULFOXIDES Ralph P. Williams, Bartlesville, Okla., assignor to Phillips Petroleum Company No Drawing. Filed Mar. 29, 1972, Ser. No. 239,317 Int. Cl. C23f 11/16 US. Cl. 252-391 7 Claims ABSTRACT OF THE DISCLOSURE Corrosion of metal surfaces in an acidic environment is reduced by the use of corrosion inhibitor compositions comprising a mixture of at least one compound selected from the group consisting of dialkyl sulfides and dialkyl sulfoxides and at least one surface-active agent.

The present invention relates to the preservation of metallic surfaces wherein the surface is in contact with an acid medium. More particularly, the invention relates to compositions and methods for inhibiting corrosion of metallic surfaces in an acidic environment.

The wastage of metals due to corrosion is an important engineering problem. Corrosion of metals can be defined as a chemical action of their environment, often resulting in their deterioration or destruction. It occurs because in many environments most metals are not inherently stable and tend to revert to some more stable combination of which the metallic ores, as found in nature, are familiar examples. Generally, it is considered that, in substantially all cases of corrosion at ordinary temperatures, the driving force of the corrosive reaction between metal and environment is electrochemical.

Corrosion inhibitors are required which protect a variety of metal in contact with cleaning solutions based on a variety of acids which are used over a wide temperature range. Acids most commonly used are sulfuric and hydrochloric; acids used for specialty applications include phosphoric, sulfamic, oxalic, tartaric, citric, acetic, and formic. The inhibitors added to these acidic environments are usually polar organic substances which function by adsorbing on the metal surface to provide a barrier film which tends to inhibit corrosion of the metal surface. Generally, the methods used to inhibit or eliminate corrosion of metals must be designed to be operative under the particular environmental conditions, i.e., the conditions of use. Particular preventive measures which are applicable in one environment are not necessarily adapted for use with the same metal under different environmental conditions.

It is an object of the invention to inhibit corrosion of metal surfaces in an acidic environment. It is another object of this invention to provide metal corrosion inhibitor compositions. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

It has now been discovered that the corrosion of metal surfaces in an acidic environment can be substantially prevented or retarded, i.e., inhibited, by incorporating into the acid medium or environment an effective, i.e., corrosion-inhibiting, amount of an additive mixture comprising at least one compound selected from the group consisting of dialkyl sulfides or dialkyl sulfoxides and at least one emulsifier or surface-active agent. The present invention is particularly applicable for the inhibition of corrosion of metals in acid cleaning and pickling baths. As used herein, the term acid bath is understood to mean the total composition, including water, acid, corrosion inhibitors, brighteners, and other additives, of the treating medium; the term acid medium is understood to mean the aqueous acid solution.

The cleaning and pickling baths in which my invention is particularly useful comprise the nonoxidizing mineral acids selected from the group consisting of sulfuric, phosphoric, hydrochloric, sulfamic, hydrofluoric and fluosilicic acids.

In carrying out the present invention, the baths are normally used at conventional concentrations of acid and at customary temperatures. Such factors are well known and can be varied as desired within the customary practice in the field.

The corrosion-inhibiting additive mixtures of the present invention comprise an essentially homogeneous mixture of at least one compound selected from the group consisting of dialkyl sulfides or sulfoxides and at least one surface-active agent. The term mixture as used herein has reference to complexes of two or more ingredients which, however thoroughly commingled, are conceived as retaining a separate existence. Mixture as used herein includes solutions, dispersions, suspensions, emulsions and the like systems having two or more components wherein no appreciable chemical reaction between the components takes place.

The dialkyl sulfides which are suitable for use in the practice of this invention are characterized by the formula wherein each R is individually selected from the group consisting of alkyl radicals having from 2 to 12 carbon atoms, preferably 3 to 8 carbon atoms. Representative of such dialkyl sulfides are diethyl sulfide, dipropyl sulfide, dibutyl sulfide, diisobutyl sulfide, dipentyl sulfide, dihexyl sulfide, dioctyl sulfide, di(2-ethylhexyl) sulfide, didodecyl sulfide, butyl hexyl sulfide, and the like. The symmetrical dialkyl sulfides are presently preferred.

The dialkyl sulfoxides which are suitable for use in the practice of this invention are characterized by the formula wherein each R is individually selected from the group consisting of alkyl radicals having from 2 to 12 carbon atoms, preferably 3 to 8 carbon atoms. Representative of such dialkyl sulfoxides are diethyl sulfoxide, dipropyl sulfoxide, dibutyl sulfoxide, diisobutyl sulfoxide, dipentyl sulfoxide, dihexyl sulfoxide, dioctyl sulfoxide, di(2-ethylhexyl) sulfoxide, didecyl sulfoxide, didodecyl sulfoxide, butyl hexyl sulfoxide, butyl Z-ethylhexyl sulfoxide, and the like. The symmetrical dialkyl sulfoxides are presently preferred.

The surface-active agents, i.e., surfactants, which are suitable for use in the practice of this invention are selected from the group consisting of rosin amines; ethoxylated rosin amines; ethoxylated aliphatic monoamines; ethoxylated derivatives of sorbitan fatty acid esters; N,N- dialkylmorpholinium alkyl sulfates; ethoxylated mercaptans; and the amphoteric product of a primary fatty acid amine and a lower olefinically unsaturated monocarboxylic acid.

The surfactants selected from the group consisting of ethoxylated aliphatic monoamines are presently preferred.

The rosin amines which are suitable for use in the practice of the invention are selected from the group consisting of the primary monoamines of the resin acids derived from oleoresin and aged stump wood. Illustrative of such resin acids are dehydroabietic acid, pimaric acid, levopimaric acid, neoabietic acid and palustric acid. Presently preferred of this group is dehydrobiethylamine, which is the monoamine derived from dehydroabietic acid.

The ethoxylated rosin amines which are suitable for use in the practice of this invention are selected from the group consisting of the ethoxylated products resulting from the ethoxylation of the aforementioned rosin amines. Generally, such ethoxylated amines will contain from 2 to about 45 ethyleneoxy units per molecule, with preferred materials containing about 4 to about 20 of such ethyleneoxy units.

The ethoxylated aliphatic amines which are suitable for use in the practice of the invention are characterized by the formula wherein R is a monovalent acyclic hydrocarbon group having from 15 to 22 carbon atoms, preferably 18 to 22 carbon atoms; and a and b are individually zero or an integer which is at least 1, at least one of a and b being an integer which is at least 1 and the sum of a and b is an integer in the range of 1 to about 20, preferably 1 to about 10. Particularly preferred are such amines wherein R is t-alkyl. The R is substituent can include mixtures of saturated and unsaturated hydrocarbon radicals such as are found in coconut oil, castor oil, soybean oil, tallow and the like.

The ethoxylated derivatives of sorbitan fatty acid esters which are suitable for use in the practice of the invention are characterized by the formula wherein each R is individually selected from the group consisting of hydrogen or the acyl radical .Rul at least one of said R groups being hydrogen and at least one of said R groups being the radical wherein R is a monovalent saturated or olefinically unsaturated hydrocarbon radical having from 11 to 21 carbon atoms; and wherein each of c, d, e and f is an integer of at least one, and the sum of c, d, e and f is an integer in the range of 4 to about 40, preferably 4 to about 20. Illustrative of these surfactants are the monolaurate, monooleate, monopalmitate, monostearate, tristearate and trioleate polyoxyethylene derivatives of sorbitan.

The ethoxylated mercaptans which are suitable for use in the practice of this invention are characterized by the formula wherein R is a monovalent hydrocarbon radical, preferably alkyl, having from 12 to 22, preferably 12 to 18, carbon atoms; and g is an integer in the range of 2 to about 20, preferably 2 to about 15.

The N,N-dialkylmorpholinium alkyl sulfate compounds which are suitable for use in the practice of this invention are characterized by the formula wherein R" is an alkyl radical containing from to 22 carbon atoms, preferably 12 to 18 carbon atoms; R is an alkyl group containing from 1 to 8, preferably 1 to 4, carbon atoms; and R is an alkyl radical containing from l to 8, preferably 1 to 4, carbon atoms. A presently preferred compound is N-cetyl-N-ethylmorpholinium ethosulfate.

The amphoteric products of primary fatty acid amines and lower olefinically unsaturated monocarboxylic acids which are suitable for use in the practice of the invention are characterized by the formula wherein Rviii is a monovalent aliphatic hydrocarbon radical containing from 10 to 22, preferably 12 to 18, carbon atoms, and R is an alkylene group containing from 2 to 7, preferably 2 to 5, carbon atoms. R" and R can be branched or unbranched. As a general rule, R is an alkyl group such as dodecyl, pentadecyl, octadecyl, and the like; R can also include mixtures of saturated and unsaturated aliphatic radicals such as coco, tallow and the like. Representative of such compounds are N- coco-3-aminopropionic acid and N-coco-3-aminobutyric acid.

The amount of corrosion inhibitor additive mixture of the present invention which is incorporated into the acid baths in accordance with this invention can vary over a wide range. Generally, the amount used will be sufficient to substantially reduce the rate of corrosion of the metal by the acid medium, without otherwise interfering with the acid function, e.g., without deleteriously affecting the cleansing and/or pickling of the metal by the acid bath. Generally, only small amounts of the additive mixture will be required. Such amounts can be on the order of about 0.01 to about 5 volume percent, based on volume of the acid medium, and preferably in the range of about 0.1 to about 1 volume percent. In general, a useful amount for any particular acid or environmental condition can easily be determined by simple test within the knowledge of those skilled in the art.

In forming the additive mixture of this invention, the dialkyl sulfide or sulfoxide component will generally comprise from to 95 weight percent, with the remaining 5 to 20 weight percent comprising surface-active agent. Particularly beneficial results are obtained with a dialkyl sulfide or sulfoxidezsurface-active agent ratio of :10, by weight.

The components of the additive mixture of the present invention can be added to, i.e., incorporated into, the acid baths individually or as an admixture. Preferably, the surface-active agent is blended into the sulfide or sulfoxide component with suflicient agitation to form a homogeneous dispersion or solution of surface-active agent in sulfide or sulfoxide and the thus-formed mixture is then added with agitation to the treating medium.

Aside from the addition of the above-described additive mixture to the acid pickling and cleaning media in accordance with this invention, the conditions of use of such acid media need not be changed. For example, the acid cleaning solutions containing the corrosion-inhibiting admixtures of the invention can be used in well stimulations in known manner, as well as pickling baths to remove rust, scale other deposits from the metal. Conventional additives, such as brightening agents, can be employed in concert with the additive mixtures of this invention. The corrosion-inhibiting additive mixtures of this invention can be employed with any nonprecious metal, such as iron, electrochemically active steel, zinc, aluminum, magnesium and alloys thereof.

The following examples exemplify the present invention.

EXAMPLE I A conventional acid treating bath comprising aqueous 10 weight percent sulfuric acid was prepared and divided into several portions. To these separate portions was added an additive mixture of the invention comprising 0.2 volume percent, based on the volume of aqueous sulfuric acid solution, of a mixture consisting of 9( weight percent dibutyl sulfide and weight percent of the specified surfactant. Following the procedure of ASTM Method D 1280-67, V2 x 3 x -inch test coupons of carbon steel were placed in static contact with the acid bath at a constant temperature. The corrosion rate for tests conducted at 150 F. for 6 hours is set forth in Table I.

TABLE I Corrosion rate, Surface-active agent mils/yr t-C18-22NH(CHgCHgo)5H 17. 2 t-Crrnz-NHCHaCHaOH 19. 8 (CHzCHzO) .H 21. 2

Cir-isCH(CHa)N o+b=3 (C H: C H10) 511 (CH CHaOMH 33. 4

n-nC w Q a+b=5 (CH1CHzO) H C0eoNHCH(C Hs) CHaCOzH Polyoxyethylene thloether .18 Polyoxyethylene sorbitan monolaurate N-cetyi-N-ethyhnorphohmum ethosultate (35% aqueous 3O 4 solution). Technical dehydroabietylamine- 20. 9 Ethoxylated technical dehydroabietylamine having 11 oxyethylene units per amino group and containing 10 percent 23 1 tree amine Control a 6, 751

Carbon steel in contact with aqueous 10 weight percent sulfuric acid containing no dibutyl sulfide or surface-active agent, for 2 hours at 150 F.

EXAMPLE II Following the procedure of Example I, the corrosion rate for carbon steel was determined at a contact time of 2 hours at 190 F. The results of this series of tests are set forth in Table I1.

Technical dehydr oabietylamine EXAMPLE III In a series of tests in which carbon steel was maintained in contact with 10 weight percent hydrochloric acid for 2 hours at 100 K, it was demonstrated that the presence of dibutyl sulfide at a concentration of 0.2 volume percent, based on the volume of aqueous hydrochloric acid, reduced the corrosion rate from 612 mils/year without dibutyl sulfide to 225 mils/year with dibutyl sulfide, a reduction of 63 percent. When, in addition to the dibutyl sulfide (in the amount specified, supra), there was present 15 weight percent, based on the weight of dibutyl sulfide, of polyoxyethylene sorbitan monolaurate surface-active agent, the corrosion rate was reduced from 612 mils/ year with no additive to 31 mils/ year with dibutyl sulfide and surface-active agent, a reduction of 95 percent. The

the uninhibited acid solution. At a concentration of 0.2

volume percent, based on volume of aqueous hydrochloric acid solution, the use of the surface-active agent alone reduced the corrosion to 146 mils/year, a 76 percent reduction from that of the uninhibited solution.

EXAMPLE IV In a series of tests in which carbon steel was maintained in contact with aqueous 10 weight percent sulfuric acid for 2 hours at 150 F., it was demonstrated that dibutyl sulfide at a concentration of 0.2 volume percent, based on volume of aqueous sulfuric acid solution, reduced the corrosion rate from 6751 mils/year (uninhibited acid solution) to 1376 mils/year with dibutyl sulfide, 1a reduction of 80 percent. When there was present 0.2 volume percent, based on volume of aqueous sulfuric acid solution, of a mixture of weight percent dibutyl sulfide and 10 weight percent of polyoxyethylene sorbitan monolaurate, the corrosion rate was reduced to 35.4 mils./ year, a reduction of 99.5 percent from that of the uninhibited solution.

EXAMPLE V In a series of tests in which carbon steel was maintained in contact with aqueous 10 weight percent hydrochloric acid for 2 hours at 190 F., it was demonstrated that dibutyl sulfoxide at a concentration of 0.2 volume percent, based on volume of aqueous hydrochloric acid solution, reduced the corrosion rate from about 78,000 mils/year (uninhibited acid solution) to a rate of 7670 mils/year. When there was present 0.2 volume percent, based on volume of aqueous hydrochloric acid solution, of a mixture of 90 weight percent dibutyl sulfoxide and 10 weight percent of an ethoxylated aliphatic amine [RNH(CH CH O) H, wherein R is a mixture of tertiary alkyl radicals having from 18 to 22 carbon atoms], the corrosion rate was reduced to 912 mils/year, a reduction of nearly 99 percent from that of the uninhibited solution.

Reasonable variations and modifications are possible within the scope of the disclosure without departing from the spirit and scope thereof.

I claim:

1. A nonoxidizing mineral acid corrosion inhibitor additive consisting essentially of an admixture of from 80 to weight percent, based on weight of said admixture, of at least one compound selected from the group having the formula wherein each R is individually selected from the group consisting of alkyl radicals having from 2 to 12 carbon atoms; and from 5 to 20 weight percent, based on weight of said admixture, of at least one surface-active agent selected from the group consisting of rosin amines; ethoxyla'ted rosin amines containing from 2 to about 45 ethyleneoxy units per mole; ethoxylated aliphatic amines characterized by the formula (CHQCHQO) H Il -N (CHaCHgOhH wherein R is a monovalent acyclic hydrocarbon group 'having from 15 to 22 carbon atoms; and a and b are individually zero or an integer having a value of at least 1, at least one of a or b being an integer having a value of at least 1, and the sum of a and b is an integer in the range of 1 to about 20;

ethoxylated derivatives of sorbitan fatty acid esters characterized by the formula wherein each R is individually selected from the group consisting of hydrogen or the acyl radical at least one of said R groups being hydrogen and at least one of said R groups being wherein R is a monovalent saturated or olefinically unsaturated hydrocarbon group having from 11 to 21 carbon atoms, and wherein each of c, d, e and f is an integer having a value of at least 1 and the sum of c, d, e and f is an integer in the range of 4 to about 40;

ethoxylated mercaptans characterized by the formula wherein R" is a monovalent hydrocarbon radical having from 12 to 22 carbon atoms and g is an integer in the range of 2 to about 20; N,N-dialkylmorpholinium alkyl characterized by the formula [RviiSOdwherein R is an alkyl radical containing from to 22 carbon atoms, R" is an alkyl radical containing sulfate compounds from 1 to 8 carbon atoms, and R is an alkyl radical containing from 1 to 8 carbon atoms; and

the amphoteric product of a primary fatty acid amine and lower olefinically unsaturated monocarboxylic acid characterized by the formula R NHR CO H wheren R is a monovalent aliphatic hydrocarbon radical containing from 10 to 22 carbon atoms and R is an alkylene group of 2 to 7 carbon atoms. 2. A corrosion inhibitor additive according to claim 1 wherein said surface-active agent has the formula References Cited UNITED STATES PATENTS 2,818,388 12/1957 Sullivan et al. 2S2Dig. 4

3,567,634 3/1971 Billings et al 252--39l 3,634,270 1/1972 Engle et al. 252149 FOREIGN PATENTS 1,042,529 9/1966 Great Britain 252-Dig. 4

CARL D. QUARFORTI-l, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R.

2l2.7 R, 2.5 R; 134-3, 41; 2528.55 E, 149, 395, Dig. 4 

